Metallic tungsten (W) has been the primary conductor for contacts in semiconductor devices. As semiconductor nodes are scaled down, the transistors and contacts become increasingly smaller. Tungsten (W) has been shown to form a highly resistive beta phase at trench dimensions of less than 15 nanometers (nm). This property of W creates a problem for advanced nodes including 7 nm and 10 nm nodes.
Cobalt has been proposed as a substitute for tungsten. However, cobalt presents additional challenges in the manufacture of semiconductor devices.